A mobile WiMAX system that applies WiMAX (Worldwide Interoperability for Microwave Access) technology, a recent focus of attention, to mobile communication involves an ASN-GW (Access Service Network Gateway) that is a service providing apparatus for providing services to an MS (Mobile Station) via a BS (Base Station). The ASN-GW is disclosed in Document “WiMAX Forum Network Architecture—Stage 3—Detailed Protocols and Procedures—Release 1.1.1, Sep. 14, 2007” for example. The ASN-GW is provided with three logical functions, namely, a Serving function for managing information of the MS, an Anchor function which serves as a data path enabling the MS to communicate, and an Authenticator function for performing authentication processing of the MS. These functions are to be executed by an ASN-GW connected to a BS to which an MS has entered.
However, there are cases in which a movement of the MS causes the three logical functions described above to be physically distributed over a plurality of ASN-GWs. For example, there are cases where a movement of the MS causes the three logical functions to be distributed over a plurality of ASN-GWs after a handover across a plurality of ASN-GWs (R4 HO: Reference-Point 4 Handover) is performed or after reauthentication subsequent to R4 HO is performed.
As an example, a case will now be cited where the three logical functions with respect to an arbitrary MS (hereinafter referred to as an MSA) are physically distributed across three ASN-GWs (an ASN-GW1 to perform the Serving function, an ASN-GW2 to perform the Authenticator function, and an ASN-GW3 to perform the Anchor function).
In such a circumstance, for example, when the ASN-GW1 enters a service suspended state, services can no longer be provided to the MSA as a WiMAX network. However, the ASN-GW2 and the ASN-GW3 are unable to detect that the ASN-GW1 has fallen into a service suspended state and, accordingly, are equally unable to detect that services can no longer be provided to the MSA. Therefore, regardless of the fact that services can no longer be provided to the MSA as a WiMAX network, the ASN-GW2 and the ASN-GW3 continue to manage information of the MSA. This causes a problem in that resources end up being secured uselessly.